From: Wei Liu <wei.liu2@citrix.com>
To: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: xen-devel <xen-devel@lists.xenproject.org>,
Kevin Tian <kevin.tian@intel.com>, Wei Liu <Wei.Liu2@citrix.com>,
Jun Nakajima <jun.nakajima@intel.com>,
Jan Beulich <JBeulich@suse.com>
Subject: Re: [PATCH] VMX: fix vmx_{find,del}_msr() build
Date: Wed, 25 Jul 2018 09:30:25 +0100 [thread overview]
Message-ID: <20180725083025.khldqe66bskmsgc5@citrix.com> (raw)
In-Reply-To: <d47221f7-6b21-026e-3a68-36253250b2e1@citrix.com>
On Tue, Jul 17, 2018 at 09:39:03AM +0100, Andrew Cooper wrote:
> On 17/07/2018 07:57, Jan Beulich wrote:
> >>>> On 16.07.18 at 18:56, <andrew.cooper3@citrix.com> wrote:
> >> On 16/07/18 17:46, Jan Beulich wrote:
> >>> For a reason that I can't explain, it is only the shim build that fails
> >>> for me with an older gcc due to the compiler not recognizing that
> >>> apparently uninitialized variables aren't really uninitialized.
> >> The only thing that comes to mind is some differences in CFLAGS et al.
> >> There is nothing in kconfig which would plausibly impact that code.
> > Oh, right - looks like the shim build inherits the tool stack's CFLAGS,
> > which specify -O0 in debug builds. Otoh I'm surprised the hypervisor
> > builds at all with -O0, so I guess I'll have to look at that in some
> > more detail, not the least because xen/Rules.mk uses += to insert
> > its own -O<n>. In any event, comparing the two object files clearly
> > suggests a difference in optimization level.
>
> Hmm - interesting. I had intended not to inherit the tools dubious
> CFLAGS setting (nothing should use O0, not even for debugging), but how
> that I think back, that probably fell through the cracks in the
> associated chaos.
>
> Nevertheless, all of our code should build at any optimisation level. I
> know from other attempts that Xen also doesn't build at O3, and we could
> do with a way to select the optimisation level, independently of debug
> settings.
I agree with what you said but unfortunately reworking the build system
is rather low on my priority list.
Wei.
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next prev parent reply other threads:[~2018-07-25 8:30 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-16 16:46 [PATCH] VMX: fix vmx_{find,del}_msr() build Jan Beulich
2018-07-16 16:56 ` Andrew Cooper
2018-07-17 6:57 ` Jan Beulich
2018-07-17 8:39 ` Andrew Cooper
2018-07-25 8:30 ` Wei Liu [this message]
2018-07-18 9:15 ` Jan Beulich
2018-07-18 9:36 ` Wei Liu
2018-07-18 9:39 ` Jan Beulich
2018-07-18 9:40 ` Wei Liu
2018-07-19 1:43 ` Tian, Kevin
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